1. Field of the Invention
This invention generally relates to an illuminated light panel which utilizes the sidelight that escapes from unsheathed fiber optic cable.
2. Description of the Prior Art
A variety of illumination techniques have been used to form light panels and back illuminated signs.
For example, U.S. Pat. No. 4,918,578 issued to Thompson discloses a device utilizing flexible strands of incandescent light bulbs for back illumination of signs. Specifically, Thompson discloses a light piping display illuminated by a flexible light string. The display includes a panel having a light scattering design. The flexible light string extends along the perimeter of the panel and illuminates the design. The flexible light string includes a plurality of spaced-apart, small incandescent glass bulbs. Such a design is too impractical to consider for use on a large format illumination panel or on a mobil illumination panel. Problems with bulb reliability, and difficulty in changing bulbs would preclude using this design in such applications.
Others have disclosed various designs that utilize fiber optics for illumination. Fiber optic technology has evolved over the past few decades to now include many distinct types of optical fibers designed for many different applications. As a result, the various optical fiber designs are not interchangable, and many such designs may not be effective or practical in any given application.
U.S. Pat. No. 4,924,612 issued to Kopelman discloses a sign illuminated with a fiber optic structure. In general, Kopelman discloses an apparatus having a light source that directs light into a light inlet portion of a fiber optic structure such that light is emitted from a light outlet portion thereof and directed onto a configuration forming structure. The Kopelman fiber optic structure can include (1) both fiber optic cable and fiber optic plastic; or (2) fiber optic plastic embodying fluorescent and/or luminescent materials. The fiber optic cable used in Kopelman is a cladded single fiber optic cable having crystalline light-conveying channels.
U.S. Pat. No. 4,422,719 to Orcutt discloses the use of a light guide comprising a single optical transmission core of clear resinous plastic having a transparent or translucent sleeve which is shrink-fitted or otherwise tightly fitted around the periphery. The sleeve substantially seals the core from the surrounding air, and is designed to laterally disperse, diffuse, or refract through its sidewall a substantial component of light transmitted along the core.
U.S. Pat. No. 5,036,435 to Tokuda et al. discloses an illumination panel including an optical fiber sheet located between a surface panel and a reflecting layer. The optical fiber sheet is formed by arranging a plurality of optical fibers which have one end optically connected to a light source. The optical fibers include a light-leaking portion on at least one surface.
The prior art illumination panels that use fiber optics offer different ways for the light from the light source to travel through and escape the optic cable. One panel (Tokuda) only allows one end of the fiber optic cable to be plugged into the light source, which causes problems with light density the further it travels from the light source. Those prior art devices that allow both ends of the cable to be plugged into the light source, all have some sort of light blocking cladding or sheathing around individual cables that are subject to some form of alteration. Some alterations are in the form of flaws such as notches in the cables which act as light-leaking portions (Tokuda) and by removing less cladding along the cable that is closer to the source of light (Chiu).
These and other prior art illumination devices that utilize fiber optics have been inadequate for use in backlighting a relatively large panel or sign, and particularly a large mobile panel or sign. In fact, prior art applications of illumination panels have been limited to relatively small scale applications. Specifically, prior art designs are adapted merely for background illumination of flat information display units such as liquid crystal display panels, text panels, military and commercial instrument panels, etc. Larger scale applications require vast amounts of light. In accordance with prior art designs, one could not obtain a sufficient amount, while maintaining a relatively thin illumination panel. In addition, prior art designs do not provide a large format illumination panel that can be mounted on a motor vehicle such that the light therefrom is non-obtrusive to other motorist.